CitroŽn g/box Crown Wheel and Pinion - Page 2 - LotusTalk - The Lotus Cars Community
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post #21 of 227 (permalink) Old 02-12-2016, 08:02 AM
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Switching to a Renault gearbox is not a cheaper solution by any stretch of the imagination. Remember that the Citroen cars have inboard rear brakes. If you change gearboxes you need to either reengineer the Renault gearbox mounts to accept the rear brakes, or change out the rear suspension to outboard brakes. Outboard brakes mean new halfshafts, new upper and lower links, as well as new rear hubs, calipers, rotors, and plumbing. And don't forget rear wheels. The offset for the rear wheels will be different with brakes crammed in there.

The shifter will need to be changed, as the Renault shifter is a two cable system with translator or a direct shift depending on the type of rear housing your Renault gearbox has, and the Citroen is a cable and shaft system.

Finally, the muffler support bracket on the Citroen cars bolts to the rear housing, along with a heat shield. Renault cars have an exhaust hanger that supports the shifter cables as well as mounts to hang the muffler. This muffler support bracket mounts to the transmission mounts, which makes an inboard brake solution that much harder to implement.

That $1,800 is looking pretty cheap now...

Mike

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post #22 of 227 (permalink) Old 02-12-2016, 08:46 AM Thread Starter
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post #23 of 227 (permalink) Old 02-12-2016, 09:10 AM
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Quote:
Originally Posted by carbuff View Post
The circular 'polish' marks to the right side of your picture are the result of crownwheel carrier bearing failure.
I think the marks in that photo are just Citroen truing up the casting, too sharp and smooth to be damage. Also within the radius of the CW.

Here's the photo your sharp eyes have pre-visualized!

Definitely agree on the Renault cost & effort, if this transaxle grenades I'd have to look at extreme measures- Audi, Subaru STi or similar swaps. Better to treat this one right (and keep my eyes out for a spare!)
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post #24 of 227 (permalink) Old 02-12-2016, 09:16 AM
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now, please mr Dangerous, don't spread any fairytales!!

I ask for a very, very nice used cwp set, wich is for the Esprit like new, because of different rotation, 1200 euro. Nowadays, 1350 USD!!

I have some brandnew original CWP sets. I ask 1800 euro.

I did have a quotation from Tandler 3 years ago. German gear manufactorer for Ferrari, Maserati, Porsche etc. 1500 euro for one set, minimum order 50 sets.


You go for it mr Dangerous.


I still can supply the Esprit community for many years with parts or complete rebuilds.


cheers,


Harry
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post #25 of 227 (permalink) Old 02-12-2016, 11:57 AM
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Quote:
Originally Posted by snowrx View Post
I think the marks in that photo are just Citroen truing up the casting, too sharp and smooth to be damage. Also within the radius of the CW.

Here's the photo your sharp eyes have pre-visualized!


I had the same "casting polishing" on the inside of my case (to the right of the pinion in the photo) and my diff carrier bearings failed in 1998. My shop said "the crownwheel was rubbing in the case".

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35K miles later, in 2012, I found the diff bearing sloppy on the CW side, so I replaced them again with the name-brand bearings (as opposed to the 'Made in Poland OEM pieces).

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post #26 of 227 (permalink) Old 02-12-2016, 12:05 PM Thread Starter
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Dear Harry,

We can not change the fact that OEM gears, if run "backwards", are inherently weaker and it doesn't matter if they are old or "fresh" from the cutter. Geometry was and still will be wrong for the application (the tooth flanks incline angle is wrong and promotes over-stress fractures).

Why waste money on making duplicates of the original inferior CWP? They still won't be "right", (still working on wrong side of the teeth,coast side is used as a drive side, which contributes to the fatigue failures).

In contrast, the new parts can be designed to withstand hi torque and internal impact, AND should be reverse-cut to allow correct gear meshing. Let's not discount the 9/35 ratio benefits, which make car more responsive and faster.

So..., clearly, we're comparing apples to oranges.


Oh, and hartelijk dank for giving me your approval to go ahead.



PS.
Additional strength can be achieved by Deep Cryogenic treatment.
Cryogenic treatment, can effectively increase gear box (or any other component) strength and durability. Actually any part can be treated, camshafts, diff carriers, heads, pistons, con rods, etc.
Cryo-service companies are more and more common and getting less expensive every day. For example in US one can get crank shaft treated for under $150 !
Cryogenic treatment, also known as cryogenic tempering or freezing, utilizes ultra-cold temperatures (-301 to - 317F) to modify the micro-structure of metals and other materials.
Cryogenic treatment promotes additional crystalline transformations in metals. Deep cryogenic freezing ultimately improves the performance of the metal parts. Improvement in durability is around 100 percent (that's double !!!). The typical increase in strength is 30 to 50 percent. As you might imagine, these results can dramatically reduce broken part expenditures.
http://www.thelotusforums.com/forums...nic-treatment/
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post #27 of 227 (permalink) Old 02-12-2016, 09:50 PM
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Dear mr DANGEROUS,

I fully understand your point and wish you all the best with your project. I would make the sets mostly for the Citroen DS and SM and will not make them work " backwards".

Cyro treatment is indeed very good option. Have myself done some work too.


cheers,

Harry
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post #28 of 227 (permalink) Old 02-13-2016, 05:30 AM
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Harry's point about making parts for the larger market is valid. The use of this gearbox by Lotus are small numbers compared to the other applications. I am not aware of any other applications that use it like the Esprit, but if there are any, they probably don't contribute much to the overall number. Add to that the number of Citroen based Esprits remaining, the number of miles they are driven, I suspect that the potential market is pretty small year to year.

Re-engineering parts these days isn't quite the chore it was in the past - all you really need is a good digital model of the parts and let computers do the conversions to swap direction of rotation for all of the surfaces involved and send it off to the NC cutter. Even so, those parts need to be tested, and those costs amortized over the number of sets you want to sell, in addition to raw material cost, machining, and any treatments you want to do once they leave the cutter. Don't forget the opportunity cost of tying up money in slow moving inventory.

I would be very surprised if you could get to a $2000 price point with fewer than 50 sets, and even if you could, who is going to finance upwards of $100k and then sit on the parts waiting for gearboxes to fail and for people to prefer your parts to Harry's?

Mike

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post #29 of 227 (permalink) Old 02-13-2016, 09:35 AM
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While it is true the diff gears are running "backwards" it doesn't seem to affect the longevity.They also run backwards in the Renault box in the Lotus AND the Delorean. What does seem to kill the gears is abuse or failure of the carrier bearings (probably from abuse). Using good fluid, changing it often and not flogging the car are all that is necessary to keep the parts going for a long time. Another point to be made, NEVER touch the adjusting nut on the carrier bearings without going through the whole pre-load check. Once disturbed and not properly reset you WILL kill the carrier bearings and then the gears. It is not necessary to remove that nut to change the seal but all too often is is turned anyway.
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post #30 of 227 (permalink) Old 02-13-2016, 12:43 PM
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NEVER touch the adjusting nut on the carrier bearings without going through the whole pre-load check. Once disturbed and not properly reset you WILL kill the carrier bearings and then the gears. It is not necessary to remove that nut to change the seal but all too often is is turned anyway.
^^^ David, that is Renault 'box advice.

The Citroen's carrier bearing preload and CW&P backlash are both adjusted by installing and re-arraigning shims.


There is no adjusting nut on the carrier bearings.

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post #31 of 227 (permalink) Old 02-13-2016, 01:07 PM Thread Starter
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Flank breakage in cylindrical and bevel gear applications typically initiates in the active flank, approximately in the middle of the active tooth height, and subsequently propagating to the tooth root of the unloaded flank side.
Crack initiation can be localized below the surface in the region between the case and core of surface-hardened gears.
This failure mode cannot be explained by known causes such as tooth root breakage or pitting. Even bevel gears in truck and
bus applications are at risk of damage from sub-surface fatigue if an optimum utilization of material is not achieved. In such
cases a balance between the flank breakage and pitting risk must be struck.

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post #32 of 227 (permalink) Old 02-14-2016, 09:00 AM
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Quote:
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^^^ David, that is Renault 'box advice.

The Citroen's carrier bearing preload and CW&P backlash are both adjusted by installing and re-arraigning shims.
If you can't figure out if your shims are innocent or guilty, you can always put them in a holding cell overnight

Sorry, just a little humor!

Scott

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post #33 of 227 (permalink) Old 02-14-2016, 10:31 AM Thread Starter
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Originally Posted by mike.griese View Post
Harry's point about making parts for the larger market is valid. The use of this gearbox by Lotus are small numbers compared to the other applications. I am not aware of any other applications that use it like the Esprit, but if there are any, they probably don't contribute much to the overall number. Add to that the number of Citroen based Esprits remaining, the number of miles they are driven, I suspect that the potential market is pretty small year to year.

Re-engineering parts these days isn't quite the chore it was in the past - all you really need is a good digital model of the parts and let computers do the conversions to swap direction of rotation for all of the surfaces involved and send it off to the NC cutter. Even so, those parts need to be tested, and those costs amortized over the number of sets you want to sell, in addition to raw material cost, machining, and any treatments you want to do once they leave the cutter. Don't forget the opportunity cost of tying up money in slow moving inventory.

I would be very surprised if you could get to a $2000 price point with fewer than 50 sets, and even if you could, who is going to finance upwards of $100k and then sit on the parts waiting for gearboxes to fail and for people to prefer your parts to Harry's?
Mike,
Where did you get the 2000 number? Did you quote it with someone else? What company?
Please read my post #4, again. Quote was based on 25 sets.

BTW, there are almost 6,100 Esprits with Citroen tranny plus a few Maseratis.

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post #34 of 227 (permalink) Old 02-14-2016, 11:15 AM
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Originally Posted by greentengu View Post
Quote:
The Citroen's carrier bearing preload and CW&P backlash are both adjusted by installing and re-arraigning shims.
If you can't figure out if your shims are innocent or guilty, you can always put them in a holding cell overnight

Sorry, just a little humor!

Scott
The Professor caught me.

Stupid Auto-Correct! LOL

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post #35 of 227 (permalink) Old 02-14-2016, 12:09 PM
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I vote guilty?
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post #36 of 227 (permalink) Old 02-14-2016, 04:01 PM
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Ha, yup! I may be a college English professor, but sadly, when it comes to my Esprit "knowledge base", I'm just a goggly-eyed middle-school kid with his Adam's apple jutting from his skinny throat, ogling the pretty girls and wishing one would talk to him !!!

Cheers,

Scott

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post #37 of 227 (permalink) Old 02-14-2016, 05:29 PM
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It's a swag. I had a set manufactured (well respected racing gearbox shop lots of experience with Citroen gearboxes yadda yadda) about 12 years ago and just making a set from old parts was well north of that. They didn't quite get it right, which meant another teardown and replacement, which is about the time we came across Harry. Which is why, from my perspective, I would not be interested in putting untried parts into a gearbox again, particularly ones that are redesigned in a significant way. The price of failure is pretty high, as you can destroy all of the other gears in the box and be out far more than another CWP. Call it once bitten, twice shy.

If you can get them done cheaper - go for it. You still have the problem with paying up front and sitting on the parts until they move - it just means the number is smaller.

Mike

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post #38 of 227 (permalink) Old 02-14-2016, 08:21 PM Thread Starter
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Well, it may be a good "winter" project I'd like to play. Building a better mouse trap is always a fun.

Just curious: is UN1 CWP also run on the coast side?

FYI: effects of lowering C35 final drive ratio from 4.375(8/35) to 4.000 (8/32) -see the chart
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post #39 of 227 (permalink) Old 02-15-2016, 08:46 AM
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"Additional strength can be achieved by Deep Cryo and REMS ISF treatments." I agree about the Cryo bit. since Im in the business...(not promoting just saying to make a point). The REMS is absolutely not TRUE. The polish level is way too high (at 1 RA) and causes the oil in the gear box to bead up. Micro polishing achieves that goal with a lower RA and of course gets rid of all the sharp edges that are sources for stress concentrations.

"Cryogenic treatment, also known as CRYOGENIC TEMPERING" Tempering is a term used in Heat treatment. It is used as a marketing tool by a shoddy individual in our industry because it sounds familiar to people. Tempering is defined in ASM's Metal Handbook as "..reheating hardened steel or hardened cast iron to some temperature below the eutectoid temperature for the purpose of decreasing hardness and increasing toughness." That is not cryogenic processing.

If you guys really want to make the bearings last then you install silicon nitride bearings or Ceramic bearings. You send your bearings in to Performancebearing.com and you probably not have to replace them for years! Their bearings burnish the races, which is a good thing. And if you cryo the races...Bobs your uncle
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post #40 of 227 (permalink) Old 02-15-2016, 10:57 AM Thread Starter
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